Urinalysis - The Kidneys & Urine Formation Flashcards
What is the functional unit of the kidney?
nephron
What does the nephron consist of?
-glomerulus
-Bowman’s capsule
-proximal convoluted tubule
-loop of Henle
-distal convoluted tubule
What are the main constituents of urine?
-water
-urea (50%)
-sodium
-chloride
What is urea?
the breakdown product of protein
What is the main function of the glomerulus?
to filter blood
What are the 3 renal functions associated with urine formation?
- filtration - takes place in the glomerulus
- reabsorption - renal tubules
- secretion - renal tubules
During urine formation, which substances are NOT allowed to filter through the glomerulus in significant amounts?
protein and cells
Where does water reabsorption take place in the nephron?
proximal and distal tubules
Where does reabsorption of glucose take place in the nephron?
proximal tubules
Which hormone controls reabsorption of water in the distal tubules?
anti-diuretic hormone (ADH)
Where is anti-diuretic hormone produced, stored, and secreted?
it is produced in the hypothalamus and stored and secreted by the posterior pituitary
Which hormone controls reabsorption of sodium?
aldosterone
Where is aldosterone produced?
adrenal cortex
What is reabsorption of sodium linked to?
excretion of potassium (K+) and hydrogen ions (H+)
What is the process by which filtered water, ions, and molecules leave the tubules for return to the blood via the peritubular capillaries?
reabsorption
What is the process by which a substance from the blood is transported across the wall of the tubule into the filtrate?
secretion
What is the glomerular filtration rate?
115-125 mL of filtrate formed per minute by the glomeruli
How much of the filtrate will the renal tubules reabsorb?
All but 1 mL of the filtrate, which will be passed in the urine
What is the renal threshold for glucose?
160-180 mg/dL
What does the proximal convoluted tubule reabsorb?
-water
-sodium
-chloride
-potassium
-urea
-glucose
-amino acids
What does the proximal convoluted tubule secrete?
hydrogen ions and medications
What does the descending limb of the Loop of Henle reabsorb?
water
What does the ascending limb of the Loop of Henle reabsorb?
sodium and chloride
What does the distal convoluted tubule reabsorb?
sodium
What does the distal convoluted tubule secrete?
hydrogen ions and potassium
What is the final site for water reabsorption to make urine more dilute or concentrated?
the collecting duct
What controls sodium and chloride reabsorption in the collecting duct?
aldosterone
In the collecting duct, how is water reabsorbed?
by osmosis and in response to ADH
Describe the renin-angiotensin-aldosterone axis.
-renin is secreted by the juxtaglomerular apparatus of the kidneys and catalyzes the conversion of angiotensin to angiotensin I
-angiotensin I stimulates the production of angiotensin II
-angiotensin II regulates renal blood by (1) constriction of renal arterioles and (2) secretion of aldosterone from the adrenal glands to facilitate retention of sodium
What is the function of parathyroid hormone in urine formation?
promotes calcium reabsorption from the filtrate into the blood and excretion of phosphate ions from the blood into the filtrate
Where is erythropoietin produced?
in the kidneys by the peritubular fibroblasts
-it stimulates RBC production in response to lowered oxygen levels
